*{
    padding: 0;
    margin: 0;
}

.boxA{
    position: absolute;
    width: 100%;
    height: 100%;
    background: linear-gradient(to right, blue, pink);
    .box{
        width: 500px;
        height: 500px;
        background: linear-gradient(to right, saddlebrown,cadetblue);
        position: absolute;
        left: 50%;
        top: 50%;
        margin: -250px 0 0 -250px;
        .header{
            display: flex;
            justify-content: center;
        }
        .cneter{
            .left{
                display: flex;
                justify-content: center;
                margin-top: 30px;
                input{
                    width: 300px;
                    height: 30px;
                    line-height: 30px;
                }
            }
        }
        .btn{
            height: 100px;
            display: flex;
            justify-content: space-around;
            align-items: center;
            button{
                width:80px;
                height: 40px;
            }
        }
    }
}